docs: def _set_mtu_to_nics(self, conf):
          """
          For all the nics of all the domains in the conf that have MTU set,
          save the MTU on the NIC definition.
  
          Args:
              conf (dict): Configuration spec to extract the domains from
  
          Returns:
              None
          """
          for dom_name, dom_spec in conf.get('domains', {}).items():
              for idx, nic in enumerate(dom_spec.get('nics', [])):
                  net = self._get_net(conf, dom_name, nic)
                  mtu = net.get('mtu', 1500)
                  if mtu != 1500:
                      nic['mtu'] = mtu